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How do you calculate amp draw on low voltage track light?

Hey Yahoo Experts! I have a halogen track light fixture. It uses a transformer to convert 120 vac to 12v. The fixture has 5 20 watt lamps. How do you calculate the amp draw? Maybe I made my question sound like a riddle, but it's not. Since the voltage was stepped down from 120 to 12, which voltage do I use to calulate the amp draw with 5 20 watt bulbs on the fixture. I don't have an amp meter.

Public Comments

  1. amps = watts / volts. 5 x 20 = 120 watts. 120 watts / 120 volts = 1 amp
  2. I'll take a WILD guess, An Amp meter? Perhaps? Rev. Steven
  3. RLA's math is a little off, but close enough to use.
  4. RLA, check your math, its off a little It's close though NEC 2005 "Art 220 - Branch-circuit, feeder, and service calcs. 220.43 -- Show window and track lighting (B) Track Lighting For track lighting in other than dwelling units or guests rooms or guests suites of hotels or motels, an additional load of 150VA shall be included for every 600mm (2 foot) of lighting track or fraction thereof. Where multicircuit track is installed, the load shall be considered to be divided equally between the track circuits"
  5. P=IE
  6. 5*20W = 100W 100W/12V = 8.33 A at 12V (0.833A at 120V) Why is this important? If the transformer came with the track it should be rated for the track load.